Scanning tunneling microscopy of Si/SiO2 interface roughness and its dependence on growth conditions

The interface between silicon (100) and thermal silicon dioxide grown by wet, dry, and trichloroethylene oxidation has been investigated by scanning tunneling microscopy and scanning tunneling spectroscopy. The scanning tunneling microscopy images of the silicon surface, after removal of oxide, reveal the presence of silicon bumps (protrusions) in samples prepared by wet and dry oxidation while no protrusions are seen at the interface of trichloroethylene oxidized samples. The spectroscopic measurements predict that these are silicon protrusions and are produced by oxide growth conditions. X-ray photon spectroscopy on samples containing protrusions also supports the above prediction. Thus, our study suggests that roughness of the silicon-silicon dioxide interface depends on oxide growth conditions and a relatively smooth interface is obtained by tricholoroethylene oxidation.